Maintaining a relatively constant and appropriate operating temperature and humidity for electronic devices is essential to obtaining a low level of failure rate. Electronic devices such as servers are mounted in rack-mount housings, and are located in suitable rooms which are air-conditioned to maintain a relatively constant temperature and humidity level in the room, and by extension, the servers and/or other electronic devices in the room. Often the rooms containing this equipment are specially designed with raised floors equipped with removable panels that have ports that open to the region beneath the raised floor. This region beneath the floor is used to provide wiring interconnections, power, and is often part of a closed conditioned air delivery system. Cooling air is delivered from the air conditioning system which is typically located elsewhere in the building, to the region underneath the flooring, and from there is guided via the ports in the flooring into the room. Typically, these ports are installed in the aisles between the rack-mount housings so that conditioned air is directed through ports in the front of the rack-mount housing, past the servers, and out into the room, where it is collected and returned to the air conditioning system.
The temperature control system for the room generally consists of a room thermostat housing a temperature sensor and a control input to determine the desired operating temperature for the room. Thus the heat from the servers, other electronics, the lighting, and the personnel in the room create a given heat load for that room, and the thermostat provides regulation at a given point in the room, based on the average heat load for the entire room. The air conditioning system is designed to take a particular heat load from the room based on an aggregate design load level. However, the temperature in the housings of the servers may be significantly higher than the average temperature in the room as measured at the thermostat. Conversely, the temperature in housings with only a few servers may be significantly lower than the average in the room, as determined at the thermostat location. Thus, while the cooling efficiency of system as a whole may be adequate, the temperature variations between individual server racks can result in less than optimal operating temperatures at the location of the server racks. Further, since the cooling air is delivered throughout the room via the ports in the flooring, and only the average temperature is evaluated at the thermostat, it is possible that more cooling air than is needed is being delivered to one server rack, and an insufficient amount is delivered to a server rack that needs it. This further results in a waste of power at the air conditioning system.
FIG. 1 shows an exemplary prior art climate controlled environment for electronic devices, such as servers. In FIG. 1, a room 100 contains a raised false floor 104. The raised false floor, in conjunction with the walls and lower floor of room 100, create an air flow plenum 101. The raised false floor 104 contains ports or openings 103 placed at predetermined locations on the floor throughout the room, through which cooling air 105 flows from an air conditioner 110. Some of the cooling air 105 (shown by arrows 106) passes through ports in heat-producing devices 141 mounted throughout a rack-mount housing 140. There may be any number of such rack-mount housings in a given room. For the sake of clarity, only one such housing 140 is shown in FIG. 1. Each rack-mount housing 140 may contain a full complement of heat-producing devices 141, or any number of such devices, including none. This variation in heat load at each localized housing can result in significantly different temperature conditions in each housing, depending on the size of the housing, the number of devices in the housing, the amount of heat generated by the devices, the volume of air passing through the housing, etc.
The heat from the heat-producing devices 141 dissipates into the cooling air that is drawn into the heat-producing devices 141 and is conducted out of the rack-mount housing 140 as heated air 107. Heated air 107 typically mixes with the cooling air 105 of room 100, thus creating ambient air 109 which is returned for recycling through air conditioner 110. Air conditioner 110 comprises a heat exchanger that removes heat from and dehumidifies the ambient air 109 and re-cycles cooling air 105 into air plenum 101. A thermostat 120 comprising a temperature sensor and a control function for setting a reference temperature for the room. Temperature sensor data and the desired room temperature setting are conveyed via wiring 121 to a master control system 130, which interprets the data and the temperature setting and provides control signals via wiring 131 to air conditioner 110.